What happened
On 26 June 2007, a British Aerospace Jetstream 4102, registration G-MAJZ, was undergoing a routine pushback from Stand 12 at Birmingham Airport. The operation, a commercial passenger flight, proceeded normally until the pushback crew encountered difficulty disconnecting the towbar from the tug. Because the ground crew were not using headsets due to them being unserviceable, communication was being conducted via hand signals.
As the aircraft was obstructing the taxiway for another departing aircraft, the commander decided to return to the stand. After communicating this intention through a series of hand signals, the pushback crew began reversing the tug toward the stand. However, the aircraft's parking brake remained applied and the nosewheel was still chocked. As the tug reversed, the nose gear collapsed forward onto the towbar, causing the downlock attachment pin to be pulled from its mounting and damaging the surrounding casing.
The investigation
The investigation examined the communication methods used during the pushback and the mechanical failure of the landing gear. It was established that the pushback crew relied on hand signals because their headsets were unserviceable. The investigation also looked into the physical connection between the Schopf F110 tug and the Tronair towbar, noting that the connection between the tug's securing pin and the towbar eye was exceptionally tight.
Investigators also reviewed the airport's operational instructions and the operator's ground manual. While the airport's instructions required the person in charge of the operation to be connected to the aircraft's internal communications system via a headset, the investigation found that conducting pushbacks using only hand signals was a common practice. Furthermore, the towbar's shear pin, designed to break under excessive turning loads, failed to break during the incident.
Findings
- The primary cause of the accident was the tug attempting to reverse the aircraft while the parking brake was still applied.
- A breakdown in communication occurred because the ground crew were not using headsets, making it difficult for the commander to convey the need to return to the stand.
- The pushback crew interpreted hand signals as an indication that the brakes were released.
- The connection between the tug and the towbar was unusually tight, contributing to the difficulty in disconnecting the equipment.
- The aircraft's shear pin did not break despite the excessive load, though investigators noted this would not have prevented the collapse.